Commit message: ipf: release unhandled packets from the batch

Since 640d4db788ed ("ipf: Fix a use-after-free error, ...") the ipf
framework unconditionally allocates a new dp_packet to track
individual fragments.  This prevents a use-after-free.  However, an
additional issue was present - even when the packet buffer is cloned,
if the ip fragment handling code keeps it, the original buffer is
leaked during the refill loop.  Even in the original processing code,
the hardcoded dnsteal branches would always leak a packet buffer from
the refill loop.

This can be confirmed with valgrind:

==717566== 16,672 (4,480 direct, 12,192 indirect) bytes in 8 blocks are definitely lost in loss record 390 of 390
==717566==    at 0x484086F: malloc (vg_replace_malloc.c:380)
==717566==    by 0x537BFD: xmalloc__ (util.c:137)
==717566==    by 0x537BFD: xmalloc (util.c:172)
==717566==    by 0x46DDD4: dp_packet_new (dp-packet.c:153)
==717566==    by 0x46DDD4: dp_packet_new_with_headroom (dp-packet.c:163)
==717566==    by 0x550AA6: netdev_linux_batch_rxq_recv_sock.constprop.0 (netdev-linux.c:1262)
==717566==    by 0x5512AF: netdev_linux_rxq_recv (netdev-linux.c:1511)
==717566==    by 0x4AB7E0: netdev_rxq_recv (netdev.c:727)
==717566==    by 0x47F00D: dp_netdev_process_rxq_port (dpif-netdev.c:4699)
==717566==    by 0x47FD13: dpif_netdev_run (dpif-netdev.c:5957)
==717566==    by 0x4331D2: type_run (ofproto-dpif.c:370)
==717566==    by 0x41DFD8: ofproto_type_run (ofproto.c:1768)
==717566==    by 0x40A7FB: bridge_run__ (bridge.c:3245)
==717566==    by 0x411269: bridge_run (bridge.c:3310)
==717566==    by 0x406E6C: main (ovs-vswitchd.c:127)

The fix is to delete the original packet when it isn't able to be
reinserted into the packet batch.  Subsequent valgrind runs show that
the packets are not leaked from the batch any longer.

Fixes: 640d4db788ed ("ipf: Fix a use-after-free error, and remove the 'do_not_steal' flag.")
Fixes: 4ea96698f667 ("Userspace datapath: Add fragmentation handling.")
Reported-by: Wan Junjie <wanjunjie@bytedance.com>
Reported-at: https://github.com/openvswitch/ovs-issues/issues/226
Signed-off-by: Aaron Conole <aconole@redhat.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
Tested-by: Wan Junjie <wanjunjie@bytedance.com>
Signed-off-by: Alin-Gabriel Serdean <aserdean@ovn.org>
CVE: CVE-2021-3905
CWE: CWE-401
Vulnerability description: A memory leak was found in Open vSwitch (OVS) during userspace IP fragmentation processing. An attacker could use this flaw to potentially exhaust available memory by keeping sending packet fragments.

Project: ovs
File: ipf.c

ipf_extract_frags_from_batch(struct ipf *ipf, struct dp_packet_batch *pb,
                             ovs_be16 dl_type, uint16_t zone, long long now,
                             uint32_t hash_basis)
{
    const size_t pb_cnt = dp_packet_batch_size(pb);
    int pb_idx; /* Index in a packet batch. */
    struct dp_packet *pkt;

    DP_PACKET_BATCH_REFILL_FOR_EACH (pb_idx, pb_cnt, pkt, pb) {
        if (OVS_UNLIKELY((dl_type == htons(ETH_TYPE_IP) &&
                          ipf_is_valid_v4_frag(ipf, pkt))
                          ||
                          (dl_type == htons(ETH_TYPE_IPV6) &&
                          ipf_is_valid_v6_frag(ipf, pkt)))) {

            ovs_mutex_lock(&ipf->ipf_lock);
            if (!ipf_handle_frag(ipf, pkt, dl_type, zone, now, hash_basis)) {
                dp_packet_batch_refill(pb, pkt, pb_idx);
            }
            ovs_mutex_unlock(&ipf->ipf_lock);
        } else {
            dp_packet_batch_refill(pb, pkt, pb_idx);
        }
    }
}